There have been conventionally used user terminal devices which display on a monitor or the like an image according to digital image data supplied from an image data supplying apparatus such as a computer. The image includes static images continuous in time. The images are continuously displayed so that the dynamic image of a work (movies or animation) can be displayed.
In the above mentioned data supplying apparatus, the digital data (unit data) of a plurality of static images which are components of dynamic images are stored in a storage device in advance. In accordance with requests from a number of user terminals, the unit data which is requested for display is sequentially read from the storage device, and supplied to the user terminals. Thus, the dynamic image is displayed on the user terminals. Since the amount of data of the dynamic image of a digitized work is generally enormous, the digital data of the dynamic image has been frequently compressed in order to reduce the capacity of the digital data by employing a data compression technique, and then stored in a storage device (for example, a hard disk device).
Furthermore, according to this data supplying apparatus, the continuous digital image data is supplied to the plurality of user terminals without being interrupted from one storage device by utilizing a difference between the speed of reading the unit data from the storage device (hard disk device) and the speed of transmitting the unit data to the user terminals. That is, assuming that the speed of reading the unit data from the storage device is T bits/second (a value obtained by dividing the size of data to be read by the sum of the maximum seek time, the maximum rotation waiting time, and the data transfer time, for example, 30M bits/second), this data reading speed T is faster than a speed D bits/second (for example, 1.5M bits/second) required for processing the unit data in the user terminal. Thus, while the unit data is being processed in one user terminal, the data supply to this user terminal is completed. Therefore, the number N of the user terminals which simultaneously process the same work can be determined in accordance with the following equation (1). EQU N=int(T/D) (1)
Where, int (x) designates a maximum integer which does not exceed x.
An image communication system has been known, as an apparatus similar to the above mentioned data supplying apparatus, which supplies digital image data in such a way that a dynamic image is simultaneously displayed on a plurality of user terminals (refer to PUPA No. 2-188082). This image communication system is adapted to fetch digital image data from one data base corresponding to the storage device, to multiplex it by a multiplexing separator, and to supply the data to a plurality of user terminals.